Rotating shafts are commonly utilized to transmit mechanical energy between power sources and power outputs. In many instances, a power source and output cannot be accurately aligned, or, these components move relative to one another during operation. In this regard, separate shafts may be connected to each component and these shafts may be interconnected with a universal joint capable of transmitting rotation from one shaft to the other when the shafts are not coaxially aligned.
A common universal joint includes a pair of U-shaped yoke members with their midpoints attached to the end of first and second shafts. The open ends of the two U-shaped yokes are positioned in a facing relationship and rotated 90° relative to one another. A cruciform connecting member extends between the legs of each U-shaped yoke. This cruciform connecting member includes four radially extending torque-bearing elements each of which may further include a bearing lined cap. Accordingly, when opposing torque bearing elements are interconnected to a U-shaped yoke, a pivotal connection is formed between the cruciform member and the shaft associated with the U-shaped yoke.
One drawback of this type of universal joint is that the internal connection geometry of the cruciform connector allows a limited range of movement between the rotational axes of the two shafts. Another drawback is the loss of rotational efficiency as the angle between the rotational axes of the two shafts increases. In this regard, as the angle between the shafts increases, a driven shaft may rotate at a pronounced non-constant velocity relative to a diving shaft, causing undesirable vibration. Furthermore, when subject to high loads, the cruciform member is susceptible to cracking between adjacent ones of the torque bearing elements due to high stress concentrations.
In order to alleviate one or more of the problems associated with cruciform-type universal joints, these joints may sometimes be replaced with ring-type universal joints. Like cruciform-type joints, ring-type joints are utilized to pivotally interconnect yoke members (e.g. U-shaped or T-shaped) attached to the ends of first and second shafts. However, as opposed to utilizing a connecting member that extends between the open ends of the yokes, an annular ring surrounds the end of each of these yokes. This annular ring will typically include four radial bores spaced at 90° intervals around its circumference for receiving torque transfer elements (i.e. trunnions) extending outward from each yoke. These trunnions may also include a bearing lined cap. When the yoke is connected to the ring member, a pivotal connection is formed between the ring member and the shaft associated with the yoke.
Due to their annular geometry, ring-type universal joints allow for greater movement between the rotational axes of the two shafts while reducing vibration. Additionally, these rings eliminate the stress concentration problem associated with cruciform members. This enables transmission of increased loads between the shafts. While allowing a greater range of movement between the shafts and providing strength benefits, ring-type joints are typically difficult to install and/or service. In this regard, the opposing trunnions of the yokes are typically press fit into the radial bores in the ring. This generally requires removing each shaft from its respective component. In some instances, split annular members or “rings” are utilized wherein each half of the ring forms one half of each of the radial bores. These split rings require simultaneous connection of the shafts. Additionally, this split design reduces the bearing strength of the ring.